Method of building corewalls for dams and similar structures



Nav. 23, 1926.

C. O. TAPPAN METHOD OF BUILDING COREWALLS FOR DAMS AND SIMILAR STRUCTURES Filed Jan. 10, 192,2 "4 Sheets-Sheet l Gralll'Line z Bed Roch Ground Line o'k' i 7b of Dam Biz/@nylon Channel n n U0 8 0 n m m m .1l 7 SZ S8 TC rn en wn .wm mn nr HARLES y0. YPBW INVENTOR.

By 62M; 7%* MMA TToRNEYs.

Nov. 23 1926.

C. O. TAPPAN METHOD 0F BUILDING COREIWALLS FOR DAMS AND SIMILAR STRUCTUDES Filed Jan. 10, 1922 BY f I ATTORNEYS.

CHA RLES OJXPPAN. INVENToR.

a. 9? a .KH MPL hei? NN ,v wrm. .w 4 w WN 1 m Nov. 23 192e. 1,608,258

c. o. TAPPAN METHOD oF BUILDING conEwALLs FDR DAMS AND SIMILAR STRUCTURES Filed Jan. 1o, 1,922 4 sheets-sheet' 5' CYHARLESOJPPAMIWENTOR Ei .7.' BY, D j l Z l MATTORNEYS.

Nav. 23 1926.

c! Q. TAPPAN METHODF BUILDING COREWALLS FOR DAMS AND SIMILAR STRUCTURES l0, 1922 4 Sheets-Sheet 4 Filed Jan.

Grauied Cui-Off' MRLESU. EPPAM INVENTOR.

BY l l I ATTORNEYS.

Patented Nov. 23, 1926.

.nuire lerares' enden-ns o. Terran,

recense l eerst erica;

Gli' NEVI YGRK, N. Y.

Y VAlnplcatlon filed Jannaiyll, 1922. Serial No.r 528,213.

My invention relates to an improved method ot' building -corewills for gdams, toundations bulkhead walls, and other similar ructures and has iorfits object toprovile unimproved method of building core-` 'walls or lcut-oft' walls tor dams foundations, bulkhead Walls, or other vstructures in the cor crate through the material overlyingthe built on the bedrock. 'f i @ther und `further objeccs ot my invention will beapparent from the following description and trom the accompanying drawings l5 ot illustrative embodiments thereof,y in

whichi i lltirure l is u general plan ot a valley showing outline ol' duin in dash lines and 'outline ot core vail in dot and dash lines; .i

Figure 2 a vertical section taken on the line 13-2 ot Figure lvlooking inthe direction ot the arrows; i

Figure 3 a vertical section taken onthe` line 3--3 ot Figure l looking in the direction of the arrows and showing completed corewall and dam;

Figure l a crosssection ot' illustrative `valley showing` excavationv and Workingl shaftI and method of completing corewall by progressive excavating,

filling; ,Y i l Figure 5 a cross-sectiontaken substantiall)r on the line 5-5 of Figure /llooking in the direction ot the arrows and showing method'ot filling the excavated portions with sections ot yconcrete bonded together to form a continuouswater-tight structure and showing in dot and dash lines former position ot' removed cap timbersV and top lagging;

40 Figure 6 a 'fragmentary horizontal section of the corewall taken substantially onl the line (56 ot'Figure l looking in the direction oit' the arrows and showingl the encavated portion lled vwith concrete. Y

Figure 7 a side elevation of a conventional drilling machine (such, for example, as a Keystone well driller) showing lthe drill in operation sinking a hole through mis-r cellrgrneous material overlaying bedrock and surrounded by a casing; Y

Figure 8 an enlarged detail oi the bottom of the drill hole showing the drill and castraction otwhich itl is ynecessary to eX-.v

timbering, ,andv

vlligure 9 the method oit applying void lill; ingn material in connection with the embodi-k ifuentillustrated;

Figure t() aplan ot oneeinbodiment oi process utilizing the void lilled Vcut-ottq r'for complete length of corewall; and

Figure 'll a plan of oneembodiment oi' process utilizing progressive void lilled cutoii's Jfor Working shaft a'ndkdriizts. lo bedrock in order that the structure may be:v

Similar reference characters referto simiparts throughout the drawings. n

The improved method ot' construction will be described in connection vwith the building ot'corewalls for earth dams. en illustretive design of such ra structure is'shown in Figures l, Q, and 3 oi the drawings in which the corewall iss'hor-.n as continuous concrete corewall l bonded into the bedrock 2 y in conjunction a water-tight impervious structure completely closing the valley to a ing water. Figure l shows an illustrative plan ofen valley in which the dam isto Abe built and indicates the location otrcorewall l, the limits of the dam proper (comprising impervious core 4 and pervious outer Secff tions 5),the original river 6, diversion'tunnell 7, and original river bed 8.] Figure 2 illustrates a cross section ot the valley lat the site of the proposed ldarn and indicates the location of the bedrock 2, ground line 3, 'top of corewall l, location ot original river bed 8, and diversion tunnel 7, through which the tion' oi river 6 is to hevdiverted during constiurction.V Figure 3 illustrates a vertical crosssection through the daml and indicates the location of bedrock 2, ground line 3? and cross section of the dam and relation ot' corewall lthereto, V'

The methods heretofore used*r Jfor constructing such a corewall or similar struc.- ture in general are as follows: v

YVV here bedrock is encountered at a inod-V erat-e depth and is overlaid With loose inatcrial either ydry orl containing an amount of water that'can bey controlled With pumps7 predetermined levelffor the pur-posent stori tvvo lines of sheet piling commonly are driven parallel to the axis of the dam and the material enclosed by the piling exca-` vated so as to form an open trench for the corevvall. When the trench is completed to bedrock, the concrete corewall is constructed and on its completion the piling is Withdrawn and the remaining space in the open trench is refilled `with carefully compacted earth. rl`hc heavy tin'ibering required fto support the sheet piling obstructs the Work of excavation and the placing of the concrete for the corewall, and also is expensive both as to time and material. By this old method, moreover, toprovide for strainsresultingfrom unequal settlementiof the rei'illed. ground andthe surrounding material, a much thicker coreivall is required than is theV case with the improved method hereinafter described, Where the concrete is placed so as to lill completely` the excavation Without disturbing the surroundingv materiali This results in a material s`aving,`both in ex cavation and in concrete.

Where the bedrock is overlaid deeply with loose, Water-bearing material or With quick sand,`it has been the practice heretofore to use caissons `with compressed air. The caisson consists of a heavy box-like structure, the bottom having cutting edges and containing a Working chamber provided With airlocks `so that air pressure can be main` tained to keep out the Water and the ma'-` terial excavated and removed` The top of the caisson is formedlgenerally of a heavy timber Yframe upon which the concrete core- Wall gradually is built, so that, as the ma` terial is removed from the Working chamber, the cutting edges of the` caisson are forcedinto the ground by the superimposed Weight, Suflicientair pressure is carried in the air chamberto prevent the infloiv ofthe surrounding material and Water, and as a resultwof the excavation inthe Working chamber `and the addition of concrete on the top, the` caisson is forced lthrough the overlying material to` bedrock,` and the Working chamber and shafts then filled With concrete. Where thelbedrock is irregular" much diilicultyis experienced in building the cutting edges of the caissonto conform to it. In the case of a long coreivall such as the structure` shown in Figures l, 2, and 3 of the drawings, a series of caissons driven side by side would be necessary and the separate sections would have tobe connected with some form of Water-tight joint after completion. This method of construction is extremely costly and slow.` l o l My improved method of construction. 'an embodiment of Which is illustrated inFigures 1l, and` 6v of the drawings, comprises excavating a Working shaft l() Yto bedrock 2 approximately on the centerl line Vof the proposed corewall 1 preferably at the point Where the rock is deepest belovv. the surface of the ground. The first excavation 1l next is run along the bedrock from Working shaft l0 ontheline of the lproposed corevvall.

The sinking of the Working shaft and the excavating may be done in any desired manner as, for example,by the methods of sinking, excavating, and timbering ordinarily used in iniining operations.- A second excavation ll then is made on the level immedi- Vately above the first excavation and timbered in usual manner, the horizontal cap i tim- Abers `lil and top lagging 13 `Which :have

formed the roof of the first excavationserving asthetloor of the second excavation.V After the second excavation is completedor simultaneously with its excavation, the concrete of the concretecorewall l` is placedin the first excavation.starting at bedrock and suitably bonded` thereto. The vertical posts lLl and sidelagging 15 of the lirst excavation `may be left in place andthe entire excavation filled with concrete. A` third excavation rthen is made on the level immediately above the second excavation and timbered in usual manner, the horizontal cap timbersl and top lagging 13 Whichvhavc formed `the roof of the second excavation serving as the floor of the third excavation.

Then the first excavation has been filled to a convenient height its roof isrem'oved, a suitable {Water-tight' bonding' channel 16 (Figure 5) is made on they top of theconcrete,\and vvhen the thirdexcavation is completed, the horizontal caps Y12 and top lagging Whicli have formed the floor `of this third excavation are removed and the second excavation filled completely `with concrete.` The working shaft is hlleduprogressively from `the `bottom as the Work progresses, and suitablyI bonded tothe adjacent concrete.` "By this method, step by step, commencing at the` bedrock, an impervious concrete cut-olif vvall is formed to the'surface of the ground, each portion of the concrete placedin the excavations being bonded toI adjacent sections thereof so as to torni a" continuous `vvatercight` cut-off..y l

lThe method above described applicablew to conditions Where bedrock is encountered at a moderate depth and Where the' overlay#` ying material does not contain more Water lim entire length of the proposed corewall, as shown in Figure 10, or constructed so as progressif/'ely to surround first the working shaft and thereafter the drifts as shown in dash lines (Figure 1l).

`Where cut-offs surrounding the excavation are required, my improved method of forming such cut-offs is as follows:

A series of cased holes 2O and 2l (Figures 9, l0, and ll) suitably located with reference to each other and the limits of the excavation first is sunk t-o bedrock by means of any suitable y,drilling apparatus, such for instance as a Keystone well drill7 22 simi lar to that illustrated in Figures 7 and 8 of the drawings and adapted to penetrate rock and boulders or other obstructions clear down to the bedrock. ln this mannerk a casing 23 consisting of wrought iron pipe or other suitable material may be' forced down, preferably simultaneously with the drilling, to surround the hole excavated by the action of the drill 24': as shown. When a series of such cased holes have'been carried to bedrock, as shown in Figure 9, a suit`- able number are fastened to a platform 25 provided with suitable lifting' devices 26. 4Containers 27 for applying the void filling material under pressure are attached to the cased holes 2O through which it is desired to force the void filling material, the suction of a suitable pump 2S is attached to cased holes 2l through which it is desired to withdraw water, so that by means of forcingl in said material through cased holes 20 and by withdrawing Water through cased holes 21 suitably located with reference thereto, preferably until said material begins to appear in the discharge from suction hole 2l, a circulation is set up and any voids in the water bearing material or quicksand are filled.

Before commencing the void filling operation the casings are withdrawn a certain predetermined distance above the bedrock. The void filling` mixture then is placed in containers 27, the covers closed and compressed air applied Vby compressor 29 through compressed air receiver 30, and by means of pump 28 suction is applied to cased holes 21. When the void filling mixture begins to be drawn through cased holes 2l, work is suspended, the casings raised to higher level, and the process repeated. In this manner, step by step, from the bedrock, a continuous series of impervious or semiimpervious Zones are formed surrounding the proposed excavation for the purpose of reducing` or preventing the flow of water into the excavation and of facilitating the work of excavation bythe consolidation of material adjacent to its boundaries.

By the above described method a cut-off is constructed either' entirely surrounding` the site of the proposed excavation before the Work is commenced as illustrated in Figure 10, or 1s constructed firstvaroun'd the working shaft l()V and next extended pro-` gressively along the line of the proposed'excavation so as to surround portions of the working drifts ll as illustrated in Figure ll'by short dash lines.

The void filling lmaterial applied by the process described above to lill the voids in the material and thereby form an impervious or semi-impervious cut-off may be composed of an inert, voidv filling substance,

or of a bonding substance and a void filling cereals, manure, fine sand, or loam selected and combined with the bonding` elements or used separately, as may be required by the character of the voids of the particular l:naterial to be treated and in such a manner as to form a void fillingl mixturev slow setting,

easy flowing, and slightly heavier than water. The rnature of the void filling substancesv selected makes it possible to control the specific gravity of the void `filling mixture. A i

lilun'ierous attempts have been made to apply grout composed of cement paste to pervious gravel and similar water bearing materials, both for the 'purpose of reducing the flow of water and to facilitate excavation. All such attempts in the past have been unsuccessful due to the fact that the grouting mixture was not sufiiciently slow setting and easy flowing and was not properly distributed through the voids in the material, with the result that large mushroom shaped zones were formed and no continuous'homogeneous cut-off was obtained capable of forming an efficient cut off -for reducing or preventing the fiow of surrounding water.

By the improved method herein described it is evident that by the use of cased holes starting from the bedrock and raised step by step as the void filling operation proceeds, and that by the introduction of the void filling material under pressure through one series of such cased holes and the appli cation of suction to other cased holes suitably placed with relation to the pressure holes so as to create a circulation of the ma terial, and that by the use of a void filling mixture or Va mixture suitably compounded of bonding substancesy and void filling substances designed to form a slow setting,

created,surrounding an excavation and re-` ducing or ,entirelygcutting olf lthe flow of `Water into said excavationfand facilitating the removal of materialpfrom the excavation bythe consolidation totthematerialsurrounding it. 4

Many modifications of y my linvention will be apparentto ,those Yskilled nthe (art` Without departing `therefrom `or Afrom lthe scope oi the claims, my invention not ibeingdiinited to the embodiments chosenfor `purposes-,olillustration but` comprising yatinethod of building' corewalls or cut-oiavalilsby drifting andgilling and ofi` using therevvitlrunder certain ,conditions a `method `etft'orniing `pro` tecting cut-oil'wallsqvvholl-y or partiallyfiimn pervious to Waten 7h at `I-claim and desireto' Asecure byfLetters Patent is: p

L `The -processmot building` underground foundations,corewalls, and cut-off Walls for dams, bulkhead Walls, and similar-,structuresmivhichrequire `to be carried v`to bedrock through earth, gravel, `or; other soft `materialto `forni a'vvater-tight cutoff, which comprises sinking a Working shaft tovbedrock, `excavatinga lirst `excavation `along the bedrock from this shaft and timbering said first excavation, removingmaterial above said first excavation and tlmberingsaid second excavation, filling said first excavation through the seoondexcavation ,with concrete bendecido ,the bedrock, ;re1noving material above ,sai d. `second ,excavati on i and timbering said thirdexcavation, lfilling said second `excavation through thethlird excavation ,with concrete `bonded to the ,concrete ot saidlirst excavation, `and step istep excavating, timbering,and filling Withconcrete `to build aicontfiiuiousl bonded conoretevall from .the bedrock ,to the desiredheiffhtt; i v

2.The` process. of building5 underground foundations,corewalls and cut-off Walls for dams, bulkhead Walls, andn similanstruc-tures which comprises .making,airstA tunnel to be filled with the, Wall ymaterial to `form `a vlaver ot the Wall, timberingthea'oof of the thrftltunnelsuiiciently to support the Weightl necessary during ,the making i of a second excavation having as a `loonthe .roof ofthe Y first excavation, makingsuch secondexcfzwa-` tion having asaliloorthe roof ofthe-first excavation, timberlng the roof of thepsecf ond excavation,suiiicientlywto support; .the

Weight` necessary during the making-of a third excavation having. as,A a floor the roof of theisecond excavation,A filling :in the ,first excavationthrough its root'` from the second excavation, and step by step excavating, tim,- bering `and filling in `,with concrete to build a continuous bondedfconorete Wall.

i ln testimony` that I1 claim Vthe foregoing, I have hereunto set Inyhand: this QSth'day of December, 1921. f A

l CHARLES to. 1 TAPPAN. 

